This invention relates to magnetoresistive heads used in magnetic recording.
Dual-stripe magnetoresistive (xe2x80x9cDSMRxe2x80x9d) read-write heads are known in the art to have a number of advantages such as facilitating improved areal recording density. FIG. 1 illustrates a read-write head comprising a slider 1 and a read-write element 2 mounted on the trailing side of a center rail 3 of slider 1. Read-write element 2 is used to read data from and write data to a magnetic disk during use.
FIG. 2a illustrates in cross section read-write element 2 along lines Axe2x80x94A. FIG. 2b illustrates in cross section read-write element 2 along lines Bxe2x80x94B.
Referring to FIG. 2a, read-write element 2 is formed on slider 1, which is formed from Al2O3xe2x80x94TiC. An Al2O3 insulating layer 12, a bottom pole layer 14 (typically a NiFe alloy), an Al2O3 insulating layer 16, a first magnetoresistive stripe 18 (typically a NiFe alloy), a first pair of exchange layers 20a, 20b and a first pair of contact layers 22a, 22b are formed on the slider material. Contact layers 22a, 22b are used to electrically contact magnetoresistive stripe 18. Exchange layers 20a, 20b are used to stabilize the domains of MR stripe 18.
An Al2O3 insulating layer 24 is formed on contact layers 22a, 22b. A second magnetoresistive stripe 26, a second pair of exchange layers 28a, 28b and a second pair of contact layers 30a, 30b are formed on Al2O3 insulating layer 24. Contact layers 30a and 30b are for electrically contacting magnetoresistive stripe 26. Exchange layers 28a and 28b stabilize the domains of MR stripe 26.
Magnetoresistive stripes 18 and 26 are used to read data from a magnetic disk in a manner well-known in the art. See, for example, U.S. Pat. No. 3,860,965, incorporated herein by reference. An insulating layer 32 (typically Al2O3) is formed on contact layers 30a, 30b and a shared pole layer 34 (typically formed from a NiFe alloy) is formed on Al2O3 insulating layer 32. Of importance, bottom pole layer 14 and shared pole layer 32 (also known as first and second shield layers, respectively) filter the magnetic field from the magnetic disk. In this way, the magnetic field from data tracks adjacent to a track being read will not interfere with magnetoresistive stripes 18 and 26.
A gap insulating layer 36 (typically Al2O3) is formed on shared pole layer 32. Formed above gap insulating layer 36 is a top pole layer 38. Shared pole layer 32 and top pole layer 38 serve as magnetic poles during writing operations.
FIG. 2b illustrates read-write element 2 in cross section along arrows Bxe2x80x94B. As can be seen, top pole 38 extends upwardly and over a copper coil structure 40 that is used to generate a magnetic field during writing. Coil structure 40 is electrically insulated from top and shared pole layers 38, 34 by insulating material 42.
Referring back to FIG. 2a, because of the uneven shape of the top surface of shared pole layer 34, the gap between the top and shared pole layers 38, 34 is curved, bending at points 3a and 34b. The shape of magnetic bits recorded in a magnetic disk by read-write head 2 is affected by the shape of the gap between top and shared pole layers 38, 34. In particular, since this gap is curved, the shape of the bits recorded in a disk therewith is curved. This curvature reduces the recording density that can be achieved. It is an object of our invention to eliminate this curvature. Eliminating the curvature in the gap permits us to increase recording density.
A method in accordance with our invention includes the steps of forming magnetoresistive stripes on a substrate, forming a shared pole layer above the magnetoresistive stripes, forming a gap layer above the shared pole layer, and forming a write pole layer above the gap layer. In accordance with one novel feature of our invention, the top surface of the shared pole layer is planarized prior to forming the gap layer. Accordingly, our invention has the effect of eliminating or substantially reducing curvature in the gap layer. Eliminating this curvature permits us to increase recording density. In one embodiment, planarization is accomplished by a mechanical-chemical planarization technique. In another embodiment, planarization is accomplished with an etch-back technique.
In one embodiment, at the conclusion of the planarization process, the roughness Ra of the shared pole layer is less than 0.1 microns, and typically less than 0.05 microns.